The present invention relates to a light waveguide feedthrough for optoelectronic modules in which a light waveguide fiber is guided hermetically sealed through a metal tubule which is fastened in an opening in the module housing wall and a method for the manufacture of light waveguide feedthroughs.
Electro-optical transducer modules for optical information technology must also have optical feedthroughs apart from electrical ones.
In particular for reasons of cost no optical plug is to be used but rather the light waveguide fiber is to be guided directly through the housing wall, and especially in the form of a connecting fiber (pigtail). This feedthrough must be hermetically sealed and mechanically stable. Due to these stated requirements, the use of adhesion is eliminated.
Heretofore several light waveguide feedthroughs or method for their manufacture were developed and to some extent also commercially applied:
Thus a hermetically sealed light waveguide fiber feedthrough through a housing wall is already known in which the light waveguide fiber is enclosed in a metal tubule which is fixed in a bore in the housing wall. The metal tubule consists herein of a material with lower melting point and higher coefficient of expansion than the light waveguide fiber and is at least in one place fused onto the light waveguide fiber. For example, see German patent document DE-OS 34 40 437.
In addition it is known to glaze the light waveguide fiber into a thin-walled metal tubule, which is soldered in a flange and welded onto the housing.
Furthermore, a glass fiber for an optic line of the information technology is known in which, so as to improve the solderability, the mechanical strength, and, in particular the optical quality, the glass fiber surface from the inside to the outside is provided with a sequence of titanium, palladium, and gold coating as disclosed in German patent document DE-OS 34 45 982.
Further, a gas-tight feedthrough of a glass fiber through the wall of a gas-tight housing of an optoelectronic module is known in which a hole of the wall is closed gas-tight through a stopper of a vacuum-tight elastic material which was inserted through pressing together under compressive strain, and in the stopper a straight-line channel enclosing the glass fiber tightly under compressive strain is applied from the housing exterior to the housing interior as disclosed in German patent document DE-PS 36 06 588.
These conventional light waveguide feedthroughs are, however, relatively complex and not hermetically tight, in particular not sufficiently mechanically stable in order to ensure the requisite impermeability over extensive periods of time.